J.P. Fernández-García

Long range effects on the optical model of 6He around the Coulomb barrier

We present an optical model (OM) analysis of the elastic scattering data of the re- actions 6 He+ 27 Al and 6 He+ 208 Pb at incident energies around the Coulomb barrier. The bare part of the optical potential is constructed microscopically by means of a double folding procedure, using the Sao Paulo prescription without any renormal- ization. This bare interaction is supplemented with a Coulomb dipole polarization (CDP) potential, which takes into account the effect of the dipole Coulomb interac- tion. For this CDP potential, we use an analytical formula derived from the semiclas- sical theory of Coulomb excitation. The rest of the optical potential is parametrized in terms of Woods-Saxon shapes. In the 6 He+ 208 Pb case, the analysis confirms the presence of long range components, in agreement with previous works. Four-body Continuum-Discretized Coupled-Channels calculations have been performed in or- der to better understand the features of the optical potentials found in the OM analysis. This study searches to elucidate some aspects of the optical potential of weakly bound systems, such as the dispersion relation and the long range (attractive and absorptive) mechanisms.

Performance of upstream interaction region detectors for the FIRST experiment at GSI

The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment at GSI has been designed to study carbon fragmentation, measuring 12C double differential cross sections (∂2σ/∂θ∂E) for different beam energies between 100 and 1000 MeV/u. The experimental setup integrates newly designed detectors in the, so called, Interaction Region around the graphite target. The Interaction Region upstream detectors are a 250 μm thick scintillator and a drift chamber optimized for a precise measurement of the ions interaction time and position on the target. In this article we review the design of the upstream detectors along with the preliminary results of the data taking performed on August 2011 with 400 MeV/u fully stripped carbon ion beam at GSI. Detectors performances will be reviewed and compared to those obtained during preliminary tests, performed with 500 MeV electrons (at the BTF facility in the INFN Frascati Laboratories) and 80 MeV/u protons and carbon ions (at the INFN LNS Laboratories in Catania).

FIRST experiment: Fragmentation of Ions Relevant for Space and Therapy

Nuclear fragmentation processes are relevant in different fields of basic research and applied physics and are of particular interest for tumor therapy and for space radiation protection applications. The FIRST (Fragmentation of Ions Relevant for Space and Therapy) experiment at SIS accelerator of GSI laboratory in Darmstadt, has been designed for the measurement of different ions fragmentation cross sections at different energies between 100 and 1000 MeV/nucleon. The experiment is performed by an international collaboration made of institutions from Germany, France, Italy and Spain. The experimental apparatus is partly based on an already existing setup made of the ALADIN magnet, the MUSIC IV TPC, the LAND2 neutron detector and the TOFWALL scintillator TOF system, integrated with newly designed detectors in the interaction Region (IR) around the carbon removable target: a scintillator Start Counter, a Beam Monitor drift chamber, a silicon Vertex Detector and a Proton Tagger for detection of light fragments emitted at large angles (KENTROS). The scientific program of the FIRST experiment started on summer 2011 with the study of the 400 MeV/nucleon 12C beam fragmentation on thin (8mm) carbon target.

Simultaneous analysis of elastic scattering and transfer/breakup channels for the 6He + 208Pb reaction at energies near the Coulomb barrier

Abstract The elastic and α-production channels for the He 6 + Pb 208 reaction are investigated at energies around the Coulomb barrier ( E lab = 14 , 16, 18, 22, and 27 MeV). The effect of the two-neutron transfer channels on the elastic scattering has been studied within the Coupled-Reaction-Channels (CRC) method. We find that the explicit inclusion of these channels allows a simultaneous description of the elastic data and the inclusive α cross sections at backward angles. Three-body Continuum-Discretized Coupled-Channels (CDCC) calculations are found to reproduce the elastic data, but not the transfer/breakup data. The trivial local polarization potential (TLP) derived from the CRC and CDCC calculations are found to explain the features found in previous phenomenological optical model calculations for this system.

Interaction of He8 with Pb208 at near-barrier energies: He4 and He6 production

The authors would like to thank the staff of the GANIL accelerator facility for providing the high-quality 8He beam. This work was supported in part by Grants No. FPA-2010-22131-CO2-01 (FINURA) and No. FPA2013-47327-C2-1-R from the Spanish Ministry of Economy and Competitiveness, UNAM-PAPIIT IA103218 (Mexico); Grant No. N202 033637 from the Ministry of Science and Higher Education of Poland; the National Science Centre of Poland under Contracts No. 2013/08/M/ST2/00257 (LEA-COPIGAL) and No. 2014/14/M/ST2/00738 (COPIN-INFN Collaboration); and Grant No. EUI2009-04163432 (EUROGENESIS) from the European Science Foundation.

Reaction Dynamics for the Systems 7Be, 8B + 208Pb at Coulomb Barrier Energies

In this contribution we describe the first results obtained for the investigation of the elastic scattering process in the reactions induced by the Radioactive Ion Beams Be and B on a Pb target at Coulomb barrier energies. The experimental data were analyzed within the framework of the optical model in order to extract the total reaction cross section. The comparison with data available in literature for reactions induced on Pb by light ions in the mass range A = 6-8 shows that the loosely-bound B has the largest reactivity.

Study of the near-barrier scattering of 8 He on 208 Pb

G. Marquinez-Duran et al. ; 6 pags., 3 figs. ; Presented at the XXXIV Mazurian Lakes Conference on Physics, Piaski, Poland, September 6–13, 2015.

Study of the Near-barrier Scattering of He-8 on Pb-208

G. Marquinez-Duran et al. ; 6 pags., 3 figs. ; Presented at the XXXIV Mazurian Lakes Conference on Physics, Piaski, Poland, September 6–13, 2015.

Coupling to continuum effects in the 6,7Li +64Zn reactions at energies around the Coulomb barrier.

The elastic scattering angular distributions for the weakly bound nuclei 6Li and 7Li on 64Zn were measured in a wide angular range at energies around the Coulomb barrier. In addition, the excitation functions of quasi-elastic scattering at backward angles were measured and the corresponding barrier distributions were derived. The experimental data were analysed within the continuum-discretized-coupled-channel method. In this contribution, we will present a detailed study concerning the effects of the break-up channels in the 6,7Li +64 Zn reactions.

Study of the break-up channel in 11Li+208Pb collisions at energies around the Coulomb barrier

We present a study of 11Li+208Pb collisions at energies around the Coulomb barrier (Elab 24.3 and 29.8 MeV), measured at the post-accelerated beam facility, ISAC II, at TRIUMF (Vancouver, Canada). A remarkably large yield of 9Li has been observed, a result that is attributed to the weak binding of the 11Li nucleus. The angular distribution of this 9Li yield, relative to the elastic one, has been analysed in terms of first-order semiclassical calculations as well as four-body and three-body Continuum-Discretized Coupled-Channels (CDCC) calculations, based on a three-body and di-neutron model of the 11Li nucleus, respectively. The calculations reproduce well the trend of the data and support the existence of a large concentration of B(E1) strength at very low excitation energies. The connection of this large B(E1) with a possible low-lying dipole resonance is discussed.